Men are most at risk for hip fracture as they grow older because of age- related loss of bone in the femur. Men with low peak bone mass are more vulnerable than those who achieved a higher peak bone mass in early adulthood. Peak bone mass and subsequent bone loss are affected by genetics, nutrition, exercise, alcohol consumption, smoking, disease, and medication use. Hypogonadal men and men treated with glucocorticoids are at markedly increased risk for spine fracture, especially as they age and bone resorption is superimposed on age-related changes. Evaluation of osteoporosis in men should include, at minimum, measurements of gonadal function (if unknown), nutritional status, calcium homeostasis, and thyroid function. Hypogonadal men should respond to testosterone replacement therapy. Men with high- turnover osteoporosis should respond to osteoclast-inhibitor therapy, and men with decreased osteoblast function should respond to stimulators of bone formation. Long-term effects of the various treatments on the rate of hip fracture are unknown, and the degree to which osteoporosis in men can be reversed is unclear.